Legality Issues with Truck Tires: Width and Height
At one time there was a federal system that governed the maximum size of truck tires. That no longer operates. Instead, a new system has come into place that varies from state to state. The laws will generally only apply to off-roaders or to those who build up their trucks. It involves ground clearances and the overall measurements of the vehicles more than the sizes of the truck tires themselves.
There’s no legal restriction on the width of the truck tires themselves, but they’re not allowed to extend beyond the fenders of the truck in virtually every state. Although well-intentioned, it’s a very inefficient law. One simple and perfectly legal way around this is to put fender flares on the truck that are wider than the trick tires. These are counted as part of the fender, so extremely wide tires are quite legitimate as long as they don’t stick out beyond the fenders.
When putting larger truck tires on a vehicle the height of the vehicle will often be altered. Although not all states have laws relating to the amount an owner can raise the height of a truck, some do. Several states only allow modifications for between 4 inches and 8 inches from the stock height, although there are no restrictions on tire size. Note that those modifications are for above and below stock height.
In a number of states, the legal height of the vehicle is dictated by its gross vehicle weight (GVW). Although this doesn’t directly affect the size of truck tires, it does effectively limit them. As an example, in Ohio if a vehicle has a GVW that’s below 4,500 pounds then the front bumper can’t be taller than 24 inches from the ground. That height increases with gross vehicle weight, up to 31 inches for trucks with a GVW over 10,000 pounds.
The above regulations do work directly with bumper height, and that’s affected by the size of the truck tires. In all states bumper height is mandated, at different heights. The intention behind this is safety, to ensure that the bumper on lifted trucks aren’t so high off the ground that they’d end up hitting the windows of another vehicle.
Although it’s unlikely to bother all but the most extreme, there are laws covering clearance under bridges. Trucks, just like big tractor-trailers, can be up to 13 feet 5 inches tall without a permit, as long as they meet the other requirements mandated by the state where the truck is registered. However, while that’s fine in theory, in practice there are other roads and areas where bridge clearance can be as low as 10 feet.
Ultimately it comes down to the laws of individual states. Some won’t allow large tires at all. Before deciding to modify the truck and go for big truck tires check the laws in your state and see what, if anything, is legal-and what is not.